The End of the Tether

It’s an elegant idea: use a satellite orbiting through Earth’s magnetic field to produce power for other satellites or a space station. But while theorists had long pointed to this possibility, no one had ever shown that it could work. This past year, NASA and the Italian Space Agency, asi, hoped to demonstrate the potential of this concept when astronauts aboard the space shuttle Columbia reeled out a five-foot-wide asi satellite attached to a 13-mile-long tether with a thickness of one- tenth of an inch. In principle, as the shuttle and satellite orbited Earth at 17,500 miles per hour, the magnetic field would push electrons down copper wires in the tether, creating an electric current. The experiment had been tried once before in 1992, but on that occasion the reel jammed. Last February 22 the same team was at it again.

Initially they were jubilant: the tether unspooled almost to its full length without a hitch. Then, suddenly, it snapped, casting adrift the satellite (which later burned up in the atmosphere) and leaving the astronauts holding just 30 feet of charred, limp tether. We didn’t have time for an immediate emotional reaction, says astronaut Jeffrey Hoffman. But that evening the shock set in. Investigators later determined that a flaw in its insulation had caused a short circuit that burned through the tether. There was a small silver lining, though: during the abortive experiment the tether generated three times as much electricity as expected.